Tanshinone IIA is superior to paricalcitol in ameliorating tubulointerstitial fibrosis through regulation of VDR/Wnt/β-catenin pathway in rats with diabetic nephropathy

Glomerulosclerosis and tubulointerstitial fibrosis (TIF) are closely involved in the development of diabetic nephropathy (DN). Moreover, the development of TIF is closely related to epithelial-to-mesenchymal transition (EMT). Tanshinone IIA (Tan) has various pharmacological effects, especially the anti-fibrotic effect. And it is mainly used in the clinical treatment of cardiovascular diseases. Currently, the protective effect of Tan on DN and its possible mechanism have not been clearly elucidated. Our previous studies illustrated that Tan could improve the EMT of HK-2 cells induced by high glucose by regulating the vitamin D receptor (VDR)/Wnt/β-catenin pathway. Here, we collected demographic information and laboratory results from the National Health and Nutrition Examination Survey (NHANES) database in order to investigate the relationship between VD and DN. Then, we established a DN model and treated DN rats with Tan and paricalcitol (Par) for 6 weeks. We subsequently compared the changes in general condition, renal function, pathological changes, and TIF-related protein expression levels of control rats, DN rats induced by STZ, DN rats with Tan at 5.4 mg/kg, DN rats with Tan at 10.8 mg/kg, and DN rats with Par at 0.054 µg/kg, to explore the effect and mechanism of Tan and Par on DN rats. The results showed that VD had a protective effect against DN in diabetic patients. And we found that Tan had a protective effect on renal fibrosis in DN rats, which was superior to Par in improving the symptoms of "three more and one less," reducing fasting blood glucose level, improving renal index, BUN/SCr, and UACR, reducing histopathological damage of kidney, and improving the expression of fibrosis-related proteins in kidney tissue by regulating VDR/Wnt/β-catenin pathway. Tan was superior to Par in ameliorating tubulointerstitial fibrosis by regulating VDR/Wnt/β-catenin pathway in rats with diabetic nephropathy.

Sacubitril/valsartan ameliorates tubulointerstitial fibrosis by restoring mitochondrial homeostasis in diabetic kidney disease

BACKGROUND

Tubulointerstitial fibrosis plays an important role in the progression of diabetic kidney disease (DKD). Sacubitril/valsartan (Sac/Val) exerts a robust beneficial effect in DKD. However, the potential functional effect of Sac/Val on tubulointerstitial fibrosis in DKD is still largely unclear.

METHODS

Streptozotocin-induced diabetic mice were given Sac/Val or Val by intragastric administration once a day for 12 weeks. The renal function, the pathological changes of tubule injury and tubulointerstitial fibrosis, as well as mitochondrial morphology of renal tubules in mice, were evaluated. Genome-wide gene expression analysis was performed to identify the potential mechanisms. Meanwhile, human tubular epithelial cells (HK-2) were cultured in high glucose condition containing LBQ657/valsartan (LBQ/Val). Further, mitochondrial functions and Sirt1/PGC1α pathway of tubular epithelial cells were assessed by Western blot, Real-time-PCR, JC-1, MitoSOX or MitoTracker. Finally, the Sirt1 specific inhibitor, EX527, was used to explore the potential effects of Sirt1 signaling in vivo and in vitro.

RESULTS

We found that Sac/Val significantly ameliorated the decline of renal function and tubulointerstitial fibrosis in DKD mice. The enrichment analysis of gene expression indicated metabolism as an important modulator in DKD mice with Sac/Val administration, in which mitochondrial homeostasis plays a pivotal role. Then, the decreased expression of Tfam and Cox IV;, as well as changes of mitochondrial function and morphology, demonstrated the disruption of mitochondrial homeostasis under DKD conditions. Interestingly, Sac/Val administration was found to restore mitochondrial homeostasis in DKD mice and in vitro model of HK-2 cells. Further, we demonstrated that Sirt1/PGC1α, a crucial pathway in mitochondrial homeostasis, was activated by Sac/Val both in vivo and in vitro. Finally, the beneficial effects of Sac/Val on mitochondrial homeostasis and tubulointerstitial fibrosis was partially abolished in the presence of Sirt1 specific inhibitor.

CONCLUSIONS

Taken together, we demonstrate that Sac/Val ameliorates tubulointerstitial fibrosis by restoring Sirt1/PGC1α pathway-mediated mitochondrial homeostasis in DKD, providing a theoretical basis for delaying the progression of DKD in clinical practice.

Correction to: YY1 inactivated transcription co-regulator PGC-1α to promote mitochondrial dysfunction of early diabetic nephropathy-associated tubulointerstitial fibrosis

The development of diabetic nephropathy (DN) could be promoted by the occurrence of tubulointerstitial fibrosis (TIF), which has a close relationship with mitochondrial dysfunction of renal tubular epithelial cells (RTECs). As a key regulator of metabolic homeostasis, Yin Yang 1 (YY1) plays an important role not only in regulating the fibrosis process but also in maintaining the mitochondrial function of pancreatic β-cells. However, it was not clear whether YY1 participated in maintaining mitochondrial function of RTECs in early DN-associated TIF. In this study, we dynamically detected mitochondrial functions and protein expression of YY1 in db/db mice and high glucose (HG)-cultured HK-2 cells. Our results showed that comparing with the occurrence of TIF, the emergence of mitochondrial dysfunction of RTECs was an earlier even, besides the up-regulated and nuclear translocated YY1. Correlation analysis showed YY1 expressions were negatively associated with PGC-1α in vitro and in vivo. Further mechanism research demonstrated the formation of mTOR-YY1 heterodimer induced by HG up-regulated YY1, the nuclear translocation of which inactivated PGC-1α by binding to the PGC-1α promoter. Overexpression of YY1 induced mitochondrial dysfunctions in normal glucose-cultured HK-2 cells and 8-weeks-old db/m mice. While, dysfunctional mitochondria induced by HG could be improved by knockdown of YY1. Finally, downregulation of YY1 could retard the progression of TIF by preventing mitochondrial functions, resulting in the improvement of epithelial-mesenchymal transition (EMT) in early DN. These findings suggested that YY1 was a novel regulator of mitochondrial function of RTECs and contributed to the occurrence of early DN-associated TIF.

Tubular TMEM16A promotes tubulointerstitial fibrosis by suppressing PGC-1α-mediated mitochondrial homeostasis in diabetic kidney disease

Tubulointerstitial fibrosis (TIF) plays a crucial role in the progression of diabetic kidney disease (DKD). However, the underlying molecular mechanisms remain obscure. The present study aimed to examine whether transmembrane member 16A (TMEM16A), a Ca2+-activated chloride channel, contributes to the development of TIF in DKD. Interestingly, we found that TMEM16A expression was significantly up-regulated in tubule of murine model of DKD, which was associated with development of TIF. In vivo inhibition of TMEM16A channel activity with specific inhibitors Ani9 effectively protects against TIF. Then, we found that TMEM16A activation induces tubular mitochondrial dysfunction in in vivo and in vitro models, with the evidence of the TMEM16A inhibition with specific inhibitor. Mechanically, TMEM16A mediated tubular mitochondrial dysfunction through inhibiting PGC-1α, whereas overexpression of PGC-1α could rescue the changes. In addition, TMEM16A-induced fibrogenesis was dependent on increased intracellular Cl-, and reducing intracellular Cl- significantly blunted high glucose-induced PGC-1α and profibrotic factors expression. Taken together, our studies demonstrated that tubular TMEM16A promotes TIF by suppressing PGC-1α-mediated mitochondrial homeostasis in DKD. Blockade of TMEM16A may serve as a novel therapeutic approach to ameliorate TIF.

Is the proximal tubule the focus of tubulointerstitial fibrosis?

Tubulointerstitial fibrosis (TIF), a common end result of almost all progressive chronic kidney diseases (CKD), is also the best predictor of kidney survival. Almost all cells in the kidney are involved in the progression of TIF. Myofibroblasts, the primary producers of extracellular matrix, have previously received a great deal of attention; however, a large body of emerging evidence reveals that proximal tubule (PT) plays a central role in TIF progression. In response to injury, renal tubular epithelial cells (TECs) transform into inflammatory and fibroblastic cells, producing various bioactive molecules that drive interstitial inflammation and fibrosis. Here we reviewed the increasing evidence for the key role of the PT in promoting TIF in tubulointerstitial and glomerular injury and discussed the therapeutic targets and carrier systems involving the PT that holds particular promise for treating patients with fibrotic nephropathy.

Title: Bioinformatic Identification of Genes Involved in Diabetic Nephropathy Fibrosis and their Clinical Relevance

Tubulointerstitial fibrosis is an important pathological feature of diabetic nephropathy that is associated with impaired renal function. However, the mechanism by which fibrosis occurs in diabetic nephropathy is unclear. Differentially expressed genes were identified from transcriptome profiles of renal tissue from diabetic patients and unilateral ureteral obstruction mice and intersected to obtain genes that may be involved in diabetic fibrosis. Biological function analysis and protein-protein interaction network analysis were performed. ROC curve and Pearson correlation analysis between hub genes were performed and glomerular filtration rate estimated. Finally, the RNA levels of hub genes were measured using real-time PCR. A total of 283 genes were identified as potentially involved in diabetic nephropathy fibrosis. TYROBP, CTSS, LCP2, LUM and TLR7 were identified as aberrantly expressed hub genes. Immune cell infiltration analysis demonstrated higher numbers of cytotoxic lymphocytes, B lineage cells, monocyte lineage cells, myeloid dendritic cells, neutrophils, and fibroblasts in the diabetic nephropathy group. The areas under ROC curves for TYROBP, CTSS, LCP2, LUM and TLR7 were 0.9167, 0.9583, 0.9917, 0.93333, and 0.9583, respectively (P < 0.001), and their correlation coefficients with estimated glomerular filtration rate were - 0.8332, - 0.752, - 0.7875, - 0.7567, and - 0.7136, respectively (P < 0.001). The RNA levels of TYROBP, CTSS, LUM and TLR7 were upregulated in high-glucose-treated human renal tubular epithelial cells (P < 0.005). Our study identified TYROBP, CTSS, LCP2, LUM and TLR7 as potentially involved in diabetic nephropathy fibrosis. Furthermore, TYROBP, CTSS, LUM and TLR7 may be associated with epithelial-mesenchymal transition of tubular epithelial cells.

Renal tubular epithelial cell necroptosis promotes tubulointerstitial fibrosis in patients with chronic kidney disease

Renal fibrosis, a common pathological manifestation of virtually all types of chronic kidney disease (CKD), ultimately predisposes patients to end-stage renal disease. However, there is no effective therapy for renal fibrosis. Our earlier studies proved that RIP3-mediated necroptosis might be an important mode of renal tubular cell death in rats with chronic renal injury. Under transmission electron microscopy (TEM), we found morphological changes in the necrosis of human renal tissue, and the percentage of necrotic cells increased significantly in patients with stages 2 and 3a CKD. Immunofluorescence analyses showed that the percentages of TUNEL⁺ /RIP3⁺ double-positive and TUNEL⁺ /MLKL⁺ double-positive tubular epithelial cells in renal tubules of patients with stages 2 and 3a CKD were significantly increased compared to those in control patients without renal disease. Immunohistochemistry analyses of renal biopsy specimens from patients with CKD revealed RIP3, MLKL, and p-MLKL upregulation in patients with stages 2 and 3a CKD, suggesting that necroptosis of renal tubular epithelial cells in CKD patients occurs, and the peak of necroptosis was in stages 2 and 3a CKD. We showed that profibrotic factor proteins (TGF-β1, Smad2 and Smad3) and fibroblast activation markers (α-SMA and Vimentin) were specifically upregulated in stage 2 and 3a CKD patients. In addition, Pearson correlation analysis showed that the percentage of necroptotic renal tubular epithelial cells was positively correlated with TGF-β1 and collagen-I. We also showed that RIP1/3 or MLKL inhibitors decreased the expression of RIP3, MLKL, TGF-β1, and Smad3 in HK-2 cells treated with TNF-α. FGF-2, α-SMA, Vimentin and FN were overexpressed in the hRIFs cultured with the supernatant of necroptotic HK-2 cells, whereas necroptosis blockers (Nec-1s, GSK'872 and NSA) and TGF-β1/Smad3 pathway antagonists (LY364947 and SIS3) reduced FGF-2, α-SMA, Vimentin and FN levels. Collectively, necroptosis of renal tubular epithelial cells in CKD patients occurs, and the peak of necroptosis was in stages 2 and 3a CKD. Renal tubular epithelial cell necroptosis mediates renal tubulointerstitial fibrosis in patients with chronic kidney disease, which is related to the TGF-β1/Smad3 signaling pathway.

YY1 inactivated transcription co-regulator PGC-1α to promote mitochondrial dysfunction of early diabetic nephropathy-associated tubulointerstitial fibrosis

The development of diabetic nephropathy (DN) could be promoted by the occurrence of tubulointerstitial fibrosis (TIF), which had a closely relationship with mitochondrial dysfunction of renal tubular epithelial cells (RTECs). As a key regulator of metabolic homeostasis, Yin Yang 1 (YY1) played an important role not only in regulating fibrosis process, but also in maintaining mitochondrial function of pancreatic β cells. However, it was not clear whether YY1 participated in maintaining mitochondrial function of RTECs in early DN-associated TIF. In this study, we dynamically detected mitochondrial functions and protein expression of YY1 in db/db mice and high glucose (HG)-cultured HK-2 cells. Our results showed that comparing with the occurrence of TIF, the emergence of mitochondrial dysfunction of RTECs was an earlier even, besides the up-regulated and nuclear translocated YY1. Correlation analysis showed YY1 expressions were negatively associated with PGC-1α in vitro and in vivo. Further mechanism research demonstrated the formation of mTOR-YY1 heterodimer induced by HG upregulated YY1, the nuclear translocation of which inactivated PGC-1α by binding to the PGC-1α promoter. Overexpression of YY1 induced mitochondrial dysfunctions in normal glucose cultured HK-2 cells and 8-week-old db/m mice. While, dysfunctional mitochondria induced by HG could be improved by knockdown of YY1. Finally, downregulation of YY1 could retard the progression of TIF by preventing mitochondrial functions, resulting in the improvement of epithelial-mesenchymal transition (EMT) in early DN. These findings suggested that YY1 was a novel regulator of mitochondrial function of RTECs and contributed to the occurrence of early DN-associated TIF .

Suppression of LMCD1 ameliorates renal fibrosis by blocking the activation of ERK pathway

Tubulointerstitial fibrosis is a common pathway of chronic kidney disease (CKD) and is closely related to the progression of CKD. LMCD1, acting as an intermediary, has been reported to play a role in cardiac fibrosis. However, its role in renal fibrosis is yet to be deciphered. Based on the GEO database, we found the expression of LMCD1 is increased in kidney tissues of CKD patients and in human proximal tubular epithelial (HK-2) cells treated with transforming growth factor-β1 (TGF-β1), suggesting that LMCD1 may be involved in tubulointerstitial fibrosis. Herein, we investigated the role of LMCD1 in mice with unilateral ureteral obstruction (UUO) and in TGF-β1-stimulated HK-2 cells. In the UUO model, the expression of LMCD1 was upregulated. UUO-induced renal histopathological changes were mitigated by knockdown of LMCD1. LMCD1 silence alleviated renal interstitial fibrosis in UUO mice by decreasing the expression of TGF-β1, fibronectin, collagen I, and collagen III. LMCD1 deficiency suppressed cell apoptosis in kidney to prevent UUO-triggered renal injury. Furthermore, LMCD1 deficiency blocked the activation of ERK signaling in UUO mice. In vitro, LMCD1 was upregulated in HK-2 cells after TGF-β1 stimulation. LMCD1 silence abrogated TGF-β1-mediated upregulation of fibrotic genes. Treatment of HK-2 cells with ERK-specific inhibitor SCH772984 and agonist TPA validated LMCD1 exerted its function via activating ERK signaling. Together, our findings suggest that inhibition of LMCD1 protects against renal interstitial fibrosis by impeding ERK activation.

Matrix metalloproteinases and tissue inhibitors of matrix metalloproteinases in kidney disease

Matrix metalloproteinases (MMPs) are a group of zinc and calcium endopeptidases which cleave extracellular matrix (ECM) proteins. They are also involved in the degradation of cell surface components and regulate multiple cellular processes, cell to cell interactions, cell proliferation, and cell signaling pathways. MMPs function in close interaction with the endogenous tissue inhibitors of matrix metalloproteinases (TIMPs), both of which regulate cell turnover, modulate various growth factors, and participate in the progression of tissue fibrosis and apoptosis. The multiple roles of MMPs and TIMPs are continuously elucidated in kidney development and repair, as well as in a number of kidney diseases. This chapter focuses on the current findings of the significance of MMPs and TIMPs in a wide range of kidney diseases, whether they result from kidney tissue changes, hemodynamic alterations, tubular epithelial cell apoptosis, inflammation, or fibrosis. In addition, the potential use of these endopeptidases as biomarkers of renal dysfunction and as targets for therapeutic interventions to attenuate kidney disease are also explored in this review.

Pirfenidone Attenuates Renal Tubulointerstitial Fibrosis through Inhibiting miR-21

BACKGROUND

Our previous studies had shown pirfenidone (PFD) not only improved tubulointerstitial fibrosis (TIF) but also inhibited the expression of microRNA-21 (miR-21) in the renal tissue of unilateral urethral obstruction (UUO) rats. This study aims to investigate whether PFD can attenuate TIF through inhibiting miR-21 in UUO rats.

METHODS

Sprague Dawley rats were divided randomly into sham-operated group, UUO group, and PFD and olmesartan (Olm) treatment groups. Samples were collected on day 14. Expression of miR-21, TGF-β1, Smad3, and Smad7 mRNA in the renal tissue was detected using real-time quantitative PCR. Immunohistochemistry was performed to assess the protein expressions of collagen III, E-cadherin, and α-SMA. Automated capillary Western blotting was used to detect the quantitative expression of TGF-β1, Smad3, p-Smad3, Smad7, collagen III, E-cadherin, and α-SMA in renal tissues. The expression of miR-21 and Smad7 mRNA and the protein levels of collagen III and α-SMA were examined in the miR-21-overexpressing cell line, NRK-52E.

RESULTS

Compared with the UUO group, both PFD and Olm inhibited renal tubular dilation, diffused epithelial cell degeneration and necrosis, and reduced renal interstitial edema, inflammatory cell infiltration, and collagen fiber deposition, while no significant difference between PFD group and Olm group. Informatics-based approaches identified Smad7 as a likely candidate for regulation by miR-21. Compared with the sham group, miR-21 expression was upregulated in the UUO group resulting in the downregulation of Smad7 expression due to degradation. The overexpression of miR-21 in the in vitro model downregulated Smad7 and promoted EMT and ECM accumulation. Protein levels of TGF-β1, Smad3, p-Smad3, collagen III, and α-SMA were upregulated, while E-cadherin protein was downregulated in the UUO group than in the sham group. PFD rather than Olm decreased the expression of miR-21 and increased the expression level of Smad7 mRNA and then inhibited the TGF-β1/Smad3 signaling pathway. Olm only downregulated the TGF-β1/Smad3 signaling pathway.

CONCLUSIONS

PFD improves TIF by downregulating the expression of miR-21, then elevating Smad7, and finally inhibiting the activation of the TGF-β1/Smad3 signaling pathway in UUO rats.

Therapeutic potential of pro-resolving mediators in diabetic kidney disease

Renal microvascular disease associated with diabetes [Diabetic kidney disease - DKD] is the leading cause of chronic kidney disease. In DKD, glomerular basement membrane thickening, mesangial expansion, endothelial dysfunction, podocyte cell loss and renal tubule injury contribute to progressive glomerulosclerosis and tubulointerstitial fibrosis. Chronic inflammation is recognized as a major pathogenic mechanism for DKD, with resident and circulating immune cells interacting with local kidney cell populations to provoke an inflammatory response. The onset of inflammation is driven by the release of well described proinflammatory mediators, and this is typically followed by a resolution phase. Inflammation resolution is achieved through the bioactions of endogenous specialized pro-resolving lipid mediators (SPMs). As our understanding of SPMs advances 'resolution pharmacology' based approaches using these molecules are being explored in DKD.

Hypoxia and chronic kidney disease: Possible mechanisms, therapeutic targets, and relevance to cats

There is mounting evidence that kidney ischaemia/hypoxia plays an important role in feline chronic kidney disease (CKD) development and progression, as well as in human disease and laboratory animal models. Ischaemic acute kidney injury is widely accepted as a cause of CKD in people and data from laboratory species has identified some of the pathways underlying this continuum. Experimental kidney ischaemia in cats results in morphological changes, namely chronic tubulointerstitial inflammation, tubulointerstitial fibrosis, and tubular atrophy, akin to those observed in naturally-occurring CKD. Multiple situations are envisaged that could result in acute or chronic episodes of kidney hypoxia in cats, while risk factors identified in epidemiological studies provide further support that kidney hypoxia contributes to spontaneously occurring feline CKD. This review evaluates the evidence for the role of kidney ischaemia/hypoxia in feline CKD and the proposed mechanisms and consequences of kidney hypoxia. As no effective treatments exist that substantially slow or prevent feline CKD progression, there is a need for novel therapeutic strategies. Targeting kidney hypoxia is one such promising approach, with therapies including those that attenuate the hypoxia-inducible factor (HIF) pathway already being utilised in human CKD.

Profibrotic mechanisms of DPP8 and DPP9 highly expressed in the proximal renal tubule epithelial cells

BACKGROUND

DPP8 and DPP9 have been demonstrated to play important roles in multiple diseases. Evidence for increased gene expression of DPP8 and DPP9 in tubulointerstitium was found to be associated with the decline of kidney function in chronic kidney disease (CKD) patients, which was observed in the Nephroseq human database. To examine the role of DPP8 and DPP9 in the tubulointerstitial injury, we determined the efficacy of DPP8 and DPP9 on epithelial-to-mesenchymal transition (EMT) and tubulointerstitial fibrosis (TIF) as well as the underlying mechanisms.

METHODS

We conducted the immunofluorescence of DPP8 and DPP9 in kidney biopsy specimens of CKD patients, established unilateral ureteral obstruction (UUO) animal model, treated with TC-E5007 (a specific inhibitor of both DPP8 and DPP9) or Saxagliptin (positive control) or saline, and HK-2 cells model.

RESULTS

We observed the significantly increased expression of DPP8 and DPP9 in the renal proximal tubule epithelial cells of CKD patients compared to the healthy control subjects. DPP8/DPP9 inhibitor TC-E5007 could significantly attenuate the EMT and extracellular matrix (ECM) synthesis in UUO mice, all these effects were mediated via interfering with the TGF-β1/Smad signaling. TC-E5007 treatment also presented reduced renal inflammation and improved renal function in the UUO mice compared to the placebo-treated UUO group. Furthermore, the siRNA for DPP8 and DPP9, and TC-E5007 treatment decreased EMT- and ECM-related proteins in TGF-β1-treated HK-2 cells respectively, which could be reversed significantly by transduction with lentivirus-DPP8 and lentivirus-DPP9.

CONCLUSION

These data obtained provide evidence that the DPP8 and DPP9 could be potential therapeutic targets against TIF.

RETRACTED: Depleting microRNA-183-3p improves renal tubulointerstitial fibrosis after acute kidney injury via SIRT1/PUMA/FOXO3a deacetylation

This article has been retracted: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy). This article has been retracted at the request of the Editor-in-Chief. Concern was raised about the reliability of the Western blot results in Figs. 2E, and 3C, which appear to have the same eyebrow shaped phenotype as many other publications tabulated here (https://docs.google.com/spreadsheets/d/149EjFXVxpwkBXYJOnOHb6RhAqT4a2llhj9LM60MBffM/edit#gid=0). The journal requested the corresponding author comment on these concerns and provide the raw data. However the authors were not able to satisfactorily fulfil this request and therefore the Editor-in-Chief decided to retract the article.

Nifuroxazide suppresses UUO-induced renal fibrosis in rats via inhibiting STAT-3/NF-κB signaling, oxidative stress and inflammation

The current work explored the influences of nifuroxazide, an in vivo inhibitor of signal transducer and activator of transcription-3 (STAT-3) activation, on tubulointerstitial fibrosis in rats with obstructive nephropathy using unilateral ureteral obstruction (UUO) model. Thirty-two male Sprague Dawley rats were assigned into 4 groups (n = 8/group) at random. Sham and UUO groups were orally administered 0.5% carboxymethyl cellulose (CMC) (2.5 mL/kg/day), while Sham-NIF and UUO-NIF groups were treated with 20 mg/kg/day of NIF (suspended in 0.5% CMC, orally). NIF or vehicle treatments were started 2 weeks after surgery and continued for further 2 weeks. NIF treatment ameliorated kidney function in UUO rats, where it restored serum creatinine, blood urea, serum uric acid and urinary protein and albumin to near-normal levels. NIF also markedly reduced histopathological changes in tubules and glomeruli and attenuated interstitial fibrosis in UUO-ligated kidneys. Mechanistically, NIF markedly attenuated renal immunoexpression of E-cadherin and α-smooth muscle actin (α-SMA), diminished renal oxidative stress (↓ malondialdehyde (MDA) levels and ↑ superoxide dismutase (SOD) activity), lessened renal protein expression of phosphorylated-STAT3 (p-STAT-3), phosphorylated-Src (p-Src) kinase, the Abelson tyrosine kinase (c-Abl) and phosphorylated nuclear factor-kappaB p65 (pNF-κB p65), decreased renal cytokine levels of transforming growth factor-β1 (TGF-β1), tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β) and monocyte chemoattractant protein-1 (MCP-1) and reduced number of cluster of differentiation 68 (CD68) immunolabeled macrophages in UUO renal tissues, compared to levels in untreated UUO kidneys. Taken together, NIF treatment suppressed interstitial fibrosis in UUO renal tissues, probably via inhibiting STAT-3/NF-κB signaling and attenuating renal oxidative stress and inflammation.

Tubular Numb promotes renal interstitial fibrosis via modulating HIF-1α protein stability

Tubulointerstitial fibrosis is the ultimate common pathway of all manners of chronic kidney disease. We previously demonstrated that specific deletion of Numb in proximal tubular cells (PTCs) prevented G2/M arrest and attenuated renal fibrosis. However, how Numb modulates cell cycle arrest remains unclear. Here, we showed that Numb overexpression significantly increased the protein level of hypoxia-inducible factor-1α (HIF-1α). Numb overexpression-induced G2/M arrest was blocked by silencing endogenous HIF-1α, subsequently downregulated the expression of cyclin G1 which is an atypical cyclin to promote G2/M arrest of PTCs. Further analysis revealed that Numb-augmented HIF-1α protein was blocked by simultaneously overexpressing MDM2. Moreover, silencing Numb decreased TGF-β1-induceded HIF-1α protein expression. While endogenous MDM2 was knocked down this reduction was reversed, indicating that Numb stabilized HIF-1α protein via interfering MDM2-mediated HIF-1α protein degradation. Interestingly, HIF-1α overexpression significantly upregulated the expression of Numb and silencing endogenous HIF-1α blocked CoCl₂ or TGF-β1-induced Numb expression. Chromatin immunoprecipitation (ChIP) assays demonstrated that HIF-1α binded to the promoter region of Numb. This binding was significantly increased by TGF-β1. Collectively, these data indicate that Numb and HIF-1α cooperates to promote G2/M arrest of PTCs, and thus aggravates tubulointerstitial fibrosis. Numb might be a potential target for the therapy of tubulointerstitial fibrosis.

CircZNF609 is involved in the pathogenesis of focal segmental glomerulosclerosis by sponging miR-615-5p

As a set of distinct syndromes, focal segmental glomerulosclerosis (FSGS) is the most common cause of adult nephrotic syndrome with diverse mechanisms. We recently found that expression of the circular RNA circZNF609 is increased in renal biopsies of lupus nephritis patients. In the present study, we aimed to determine whether circZNF609 participates in the pathogenesis of FSGS in mice given Adriamycin. In FSGS mice, circZNF609 was upregulated while miR-615-5p was downregulated in FSGS mice analyzed by qPCR and fluorescence in situ hybridization (FISH). Expression of podocyte proteins Wilms tumor 1 (WT1) and podocin were decreased, while expression of collagen 1 (COL1) and transforming growth factor-beta1 (TGF-β1) were increased on Western blotting. Renal circZNF609 levels were positively correlated and miR-615-5p levels were negatively correlated with the degree of podocyte injury and renal fibrosis. Importantly, circZNF609 and miR-615-5p co-localized to glomeruli and tubules on FISH. Perfect match seeds were found between circZNF609 and miR-615-5p and COL1 mRNA, leading us to explore mechanisms of circZNF609 in bovine serum albumin (BSA) stimulating HK-2 cells, which model the toxicity of proteinuria on tubular cells. In vitro studies, circZNF609 increased and miR-615-5p decreased after BSA treatment and were negatively correlated with each other. COL1 and TGF-β1 were both upregulated and negatively correlated with miR-615-5p. Lastly, circZNF609 expression increased in glomeruli and tubules of FSGS patient renal biopsies. We conclude that circZNF609 may play an important role in FSGS by sponging miR-615-5p.

Serotonin 5HT2A receptor antagonism mediated anti-inflammatory and anti-fibrotic effect in adriamycin-induced CKD in rats

A selective 5-HT2A receptor antagonist ketanserin has been used preclinically to improve renal blood flow because of its beneficial effect on autoregulation in various chronic kidney disease models. Ketanserin might be able to turn down adriamycin-induced chronic kidney disease, which is characterized by renal fibrosis, inflammation and structural and functional changes in glomeruli. In the present study, we investigated whether ketanserin suppresses these renal alterations or not. Wistar rats were administered with a single dose of adriamycin (6 mg/kg/i.v), which leads to development of severe tubulointerstitial fibrosis with altered renal function. Subsequent ketanserin treatment (5 mg/kg/p.o) for 4 weeks shown significant change in oxidative stress, serum and urine parameters in adriamycin-induced chronic kidney disease rats. Additionally, results showed that mRNA expression of TGF-β and collagen IV, which are known to promote fibrosis via various signaling pathways involved in the progression of renal disease, was suppressed by ketanserin treatment. Furthermore, expression levels of 5-HT2A and pro-inflammatory marker IL-6 have also been reduced significantly after ketanserin administration in adriamycin-treated animals. Moreover, histopathological studies also reveal the considerable structural changes after ketanserin treatment, and these results are further supported via data obtained from the percentage of glomeruli size changes. In conclusion, ketanserin reduces renal fibrosis and inflammation in adriamycin-induced chronic kidney disease by suppressing 5-HT2A, IL-6, TGF-β and collagen IV expression in renal tissue.

Saroglitazar attenuates renal fibrosis induced by unilateral ureteral obstruction via inhibiting TGF-β/Smad signaling pathway

Obstructive nephropathy is a common clinical case that causes chronic kidney disease and ultimately progresses to end-stage renal disease. The activation of peroxisome proliferator-activated receptor-α (PPAR-α) reduces tubulointerstitial fibrosis and inflammation associated with obstructive nephropathy.

AIMS

This study was carried out to investigate the potential effect of saroglitazar, dual PPAR-α/γ agonist, in alleviating renal fibrosis induced by unilateralureteral obstruction (UUO).

MAIN METHODS

Twenty-four male Sprague Dawley rats were haphazardly divided into four groups of six rats each, including sham operated group, vehicle- or saroglitazar-treated UUO and saroglitazar groups. Rats received oral gavage of saroglitazar (3 mg/kg/day) for 13 days. On day 14, all rats were sacrificed; blood and renal tissues were collected.

KEY FINDINGS

Saroglitazar inhibited UUO-induced oxidative stress; it decreased the elevated levels of MDA and nitric oxide and increased levels of GSH and SOD in renal tissue. Moreover, saroglitazar repressed UUO-induced inflammation; it decreased the renal levels of nuclear factor kappa B (NF-κB) and interleukin-6 (IL-6). Furthermore, saroglitazar inhibited the accumulation of extracellular matrix via decreasing collagen, hydroxylproline and matrix metalloproteinase-9 (MMP-9) levels. Saroglitazar also decreased the expression of both the alpha smooth muscle actin (α-SMA) and tumor growth factor-beta (TGF-β). These effects were in parallel with reduction in mothers against decapentaplegic homolog 3 (smad3) expression and plasminogen activator inhibitor-1 (PAI-1) levels.

SIGNIFICANCE

Collectively, the protective impact of saroglitazar might be attributed to its antioxidant, anti-inflammatory and anti-fibrotic effects against UUO-induced tubulointerstitial fibrosis through its regulatory effect on TGF-β1/Smad3 signaling pathway.

1,25(OH)2D3 provides protection against diabetic kidney disease by downregulating the TLR4-MyD88-NF-κB pathway

The over-activation of Toll-like receptors (TLRs) is a typical immune response to injury. Previous work has suggested that controlling the over-activation of TLR4-MyD88-NF-κB may represent a new therapeutic option for diabetic kidney disease (DKD). 1,25(OH)₂D₃ has also been shown to exert a protective effect on DKD, although the mechanism involved has yet to be elucidated. The aim of this study was to investigate whether 1,25(OH)₂D₃ protects against DKD by down-regulating the innate immune TLR-NF-κB pathway. NRK-52E cells were cultured under normal or high-glucose conditions. We then used siRNA to knock down TLR4 expression under high-glucose conditions. NRK-52E cells cultured under high-glucose conditions, and streptozotocin (STZ)-induced diabetic rats, were treated with different doses of 1,25(OH)₂D₃ and used as in vitro and in vivo models, respectively. Renal biochemical indicators were then measured to evaluate the influence of 1,25(OH)₂D₃ treatment on DKD in diabetic rats. Histological analysis was also performed to determine the extent of infiltration by inflammatory cells and tubulointerstitial fibrosis. Using RT-qPCR, western blotting, immunohistochemistry and immunofluorescence, we determined the expression levels of TLR4, MyD88, NF-κB p65, MCP-1 and α-SMA to investigate whether 1,25(OH)₂D₃ could reduce the development of tubulointerstitial fibrosis. Knocking down TLR4 abolished the tubulointerstitial fibrosis caused by high-glucose conditions. High doses of 1,25(OH)₂D₃ consistently reduced the expression of TLR4-MyD88-NF-κB in NRK-52E cells. Moreover, high doses of 1,25(OH)₂D₃ had an obvious protective effect on kidney injury and inhibited the infiltration of inflammatory cells and tubulointerstitial fibrosis in diabetic rats. In conclusion, high doses of 1,25(OH)₂D₃ protected against tubulointerstitial fibrosis both in vitro and in vivo by downregulating the expression of TLR4-MyD88-NF-κB.

P-selectin blockade ameliorates lupus nephritis in MRL/lpr mice through improving renal hypoxia and evaluation using BOLD-MRI

BACKGROUND

Lupus nephritis is one of the most common and severe complications of systemic lupus erythematosus, of which poor prognosis is indicated by aggravated renal hypoxia and tubulointerstitial fibrosis. Cell adhesion molecules play a key role in the progression of lupus nephritis tubulointerstitial lesion, including P-selectin, which mediates the rolling of leukocytes and subsequent adhesion and infiltration and then initiates the inflammatory immune response and ischemia and hypoxia injury. However, the effects and mechanisms of P-selectin in lupus nephritis remain to be investigated, and a noninvasive measurement of lupus nephritis tubulointerstitial hypoxia and fibrosis remains to be explored.

METHODS

Thirty-four MRL/lpr mice were randomly divided into the following three groups: MRL/lpr, saline, and anti-P-selectin, which consisted of no treatment, treatment with normal saline, and treatment with anti-P-selectin monoclonal antibody (mAb) from 12 to 16 weeks of age, respectively. Ten male C57BL/6 mice of the same age served as normal controls. 24-h urinary protein, urinary albumin-creatinine ratio, and periodic acid-Schiff were used to assess kidney damage; Western blot or immunohistochemical staining of the hypoxia probe Hypoxyprobe™-1, hypoxia-inducible factor 1α (HIF-1α), and CD31 were used to evaluate hypoxia in renal tissue; and NADPH oxidase subunit gp91phox and p22phox were used to examine renal oxidative stress. The correlation between kidney injury and blood oxygen level-dependent magnetic resonance imaging (BOLD-MRI) was calculated to assess the clinical value of BOLD-MRI.

RESULTS

P-selectin is upregulated in lupus nephritis. Blocking P-selectin with mAb alleviated renal tubulointerstitial fibrosis, renal hypoxia, and peritubular capillary loss, without alteration of the levels of lupus activity indicators, anti-dsDNA antibody, or complement C3. BOLD-MRI showed that the reduced R2* values in the renal cortex and medulla of lupus mice were increased when treated with anti-P-selectin mAb as compared with those treated with normal saline, which were negatively correlated with Hypoxyprobe™-1 hypoxia probe and the expression of HIF-1α.

CONCLUSIONS

Early intervention of lupus nephritis with anti-P-selectin mAb can significantly improve the hypoxic state of the kidney and reduce the severity of tubulointerstitial lesions. BOLD-MRI techniques are noninvasive and can dynamically evaluate the changes in renal lesions and intrarenal oxygenation levels before and after treatment in lupus nephritis.

Autophagy in kidney disease: Advances and therapeutic potential

Autophagy is a highly conserved intracellular catabolic process for the degradation of cytoplasmic components that has recently gained increasing attention for its importance in kidney diseases. It is indispensable for the maintenance of kidney homeostasis both in physiological and pathological conditions. Investigations utilizing various kidney cell-specific conditional autophagy-related gene knockouts have facilitated the advancement in understanding of the role of autophagy in the kidney. Recent findings are raising the possibility that defective autophagy exerts a critical role in different pathological conditions of the kidney. An emerging body of evidence reveals that autophagy exhibits cytoprotective functions in both glomerular and tubular compartments of the kidney, suggesting the upregulation of autophagy as an attractive therapeutic strategy. However, there is also accumulating evidence that autophagy could be deleterious, which presents a formidable challenge in developing therapeutic strategies targeting autophagy. Here, we review the recent advances in research on the role of autophagy during different pathological conditions, including acute kidney injury (AKI), focusing on sepsis, ischemia-reperfusion injury, cisplatin, and heavy metal-induced AKI. We also discuss the role of autophagy in chronic kidney disease (CKD) focusing on the pathogenesis of tubulointerstitial fibrosis, podocytopathies including focal segmental glomerulosclerosis, diabetic nephropathy, IgA nephropathy, membranous nephropathy, HIV-associated nephropathy, and polycystic kidney disease.

Vasoactive intestinal peptide infusion reverses existing renal interstitial fibrosis via a blood pressure independent mechanism in the rat

Dialysis requiring renal failure is a silent epidemic. Despite an annual mortality of 24% the dialysis population has increased by 1-4% per annum. Regardless of the initial injury, tubulointerstitial fibrosis is a feature of the renal pathology and it inversely correlates with declining renal function. Current agents display little efficacy against tubulointerstitial fibrosis. Clearly, therapies effective against tubulointerstitial fibrosis and able to preserve kidney function are needed. Vasoactive intestinal peptide (VIP) has been shown to reverse pre-existing cardiac fibrosis. We sought to determine whether VIP is effective in tubulointerstitial fibrosis. Spontaneous hypertensive rats (SHR) on a 2.2% salt diet were randomised to zero time control, 4 week infusion of VIP (5 pmol/kg/min) or vehicle control infusion. A fourth group, to match the blood pressure reduction achieved in the VIP infused group was included. Fibrosis was quantitated by computerised histomorphometry, changes in pro-fibrotic mediators were measured by quantitative rt-PCR and macrophage activation assessed by cyclic adenosine monophosphate (c-AMP) response to incubation with VIP. Tubulointerstitial fibrosis in the VIP treated rats was significantly lower than the zero time control (P < 0.0005), the vehicle infused control (P < 0.0005) and the blood pressure matched group (P < 0.01). Although all six profibrotic mediators increased over the 4 week experimental period VIP infusion only decreased tumour necrosis alpha (TNFα) expression significantly (P < 0.001). Incubation of RAW264 macrophages with VIP significantly increased c-AMP (P < 0.01). We conclude that VIP infusion reversed existing tubulointerstitial fibrosis suggesting a possible therapeutic role for a VIP based therapy in chronic kidney disease.

Schisandrin B attenuates renal fibrosis via miR-30e-mediated inhibition of EMT

Tubulointerstitial fibrosis (TIF) is the main pathologic feature of end-stage renal disease. Epithelial-mesenchymal transition (EMT) of proximal tubular cells (PTCs) is one of the most significant features of TIF. MicroRNAs play critical roles during EMT in TIF. However, whether miRNAs can be used as therapeutic targets in TIF therapy remains undetermined. We found that miR-30e, a member of the miR-30 family, is deregulated in TGF-β1-induced PTCs, TIF mice and human fibrotic kidney tissues. Moreover, transcription factors that induce EMT, such as snail, slug, and Zeb2, were direct targets of miR-30e. Using a cell-based miR-30e promoter luciferase reporter system, Schisandrin B (Sch B) was selected for the enhancement of miR-30e transcriptional activity. Our results indicate that Sch B can decrease the expression of snail, slug, and Zeb2, thereby attenuating the EMT of PTCs during TIF by upregulating miR-30e, both in vivo and in vitro. This study shows that miR-30e can serve as a therapeutic target in the treatment of patients with TIF and that Sch B may potentially be used in therapy against renal fibrosis.

FoxO1-mediated inhibition of STAT1 alleviates tubulointerstitial fibrosis and tubule apoptosis in diabetic kidney disease

Background

Tubulointerstitial fibrosis (TIF) plays an important role in the progression of diabetic kidney disease (DKD). Forkhead box O1 (FoxO1) is involved in the regulation of metabolism and cell apoptosis, but its function in renal TIF induced by DKD is less well understood.

Methods

Human kidney biopsies with DKD and normal controls were used to detect apoptosis and TIF induced by diabetes. A mouse model with kidney-specific overexpression of Pax2-3aFoxO1 was established to further investigate the functions of FoxO1 in vivo. The in vitro roles of FoxO1 were analyzed in HK-2 cells with 3aFoxO1-knockin (3aFoxO1-KI) or FoxO1-knockdown (FoxO1-KD) via CRISPR/Cas9. Western blot, immunohistochemistry, and chromatin immunoprecipitation were used to explore the underlying mechanisms.

Findings

In this study, DKD patients had increased renal TIF and apoptosis. In vivo study showed that kidney-specific overexpression of Pax2-3aFoxO1 significantly reduced the expression of p-STAT1 with resultant renal functional impairment, retarding renal TIF and apoptosis in diabetic mice. Meanwhile, We observed that FoxO1-KD in HK-2 cells aggravated the expression of p-STAT1, leading to activation of epithelial-to-mesenchymal transition (EMT) and intrinsic apoptotic pathway. Conversely, EMT and apoptosis were significantly attenuated in HK-2 cells with 3aFoxO1-KI under hyperglycemic conditions.

Interpretation

Taken together, these data suggest that the protection role of FoxO1 against renal TIF and apoptosis in DKD is likely in part to target STAT1 signaling, which may be a promising strategy for long-term treatment of DKD.

Fund

This work was supported by grants from the National Natural Science Foundation of China (grant numbers: 81570746 and 81770812).

Oxidative Stress and Renal Fibrosis: Mechanisms and Therapies

Oxidative stress results from the disruption of the redox system marked by a notable overproduction of reactive oxygen species. There are four major sources of reactive oxygen species, including NADPH oxidases, mitochondria, nitric oxide synthases, and xanthine oxidases. It is well known that renal abnormalities trigger the production of reactive oxygen species by diverse mechanisms under various pathologic stimuli, such as acute kidney injury, chronic kidney disease, nephrotic syndrome, and metabolic disturbances. Mutually, accumulating evidences have identified that oxidative stress plays an essential role in tubulointerstitial fibrosis by myofibroblast activation as well as in glomerulosclerosis by mesangial sclerosis, podocyte abnormality, and parietal epithelial cell injury. Given the involvement of oxidative stress in renal fibrosis, therapies targeting oxidative stress seem promising in renal fibrosis management. In this review, we sketch the updated knowledge of the mechanisms of oxidative stress generation during renal diseases, the pathogenic processes of oxidative stress elicited renal fibrosis and treatments targeting oxidative stress during tubulointerstitial fibrosis and glomerulosclerosis.

DCR2, a Cellular Senescent Molecule, Is a Novel Marker for Assessing Tubulointerstitial Fibrosis in Patients with Immunoglobulin A Nephropathy

BACKGROUND/AIMS

Stress-induced cell senescence, which contributes to cell cycle arrest and is independent of age, plays an important role in chronic kidney disease (CKD) progression. DcR2, as a senescent marker, exclusively expressed in senescent tubular epithelia. The objective of this study was to examine whether urinary DcR2 (uDcR2) could be a potential biomarker for tubulointerstitial fibrosis (TIF) in patients with immunoglobulin A nephropathy (IgAN).

METHODS

This study included 210 IgAN patients and 80 healthy volunteers, with uDcR2 levels measured using enzyme-linked immunosorbent assay. We examined the relationship among uDcR2/Cr levels, renal function, and pathological parameters, using regression analysis to identify risk factors for TIF and the area under the curve (AUC) approach to predict TIF. Renal DcR2 expression was quantified by immunohistochemistry. Co-expression of DcR2 with fibrotic markers (α-smooth muscle actin [α-SMA], collagen III) was analyzed by confocal microscopy.

RESULTS

Levels of uDcR2/Cr were significantly higher in IgAN patients and in those with more severe TIF, compared with healthy controls. Serum DcR2 levels were similar across groups. The proportion of IgAN patients with stages 1-2 CKD and T0 was highest among those with uDcR2/Cr <130 ng/g. In contrast, the majority of those with uDcR2/Cr >201 ng/g had stages 4-5 CKD and T2. Levels of uDcR2/Cr were positively associated with urinary albumin to creatinine ratio (ACR), urinary N-acetyl-β-D-glucosaminidase (uNAG)/Cr, and TIF scores and negatively associated with estimated glomerular filtration rate (eGFR). uDcR2/Cr, uNAG, ACR, and eGFR were independent predictors for TIF, with AUC of 0.907 for uDcR2/Cr. This AUC value was higher than that observed for eGFR, uNAG/Cr, or ACR. The sensitivity and specificity of uDcR2/Cr in predicting TIF were 87.0 and 80.5%, respectively. Moreover, uDcR2/Cr levels were positively associated with the percentage of renal DcR2 expression. Renal DcR2 co-localized with α-SMA and collagen III in the kidneys of IgAN patients.

CONCLUSIONS

Levels of uDcR2/Cr were closely associated with the severity of TIF and renal function parameters. uDcR2/Cr represents a potential biomarker for predicting TIF in IgAN patients.

Hypoxia and Renal Tubulointerstitial Fibrosis

Hypoxia, one of the most common causes of kidney injury, is a key pathological condition in various kidney diseases. Renal fibrosis is the terminal pathway involved in the continuous progression of chronic kidney disease (CKD), characterized by glomerulosclerosis and tubulointerstitial fibrosis (TIF). Recent studies have shown that hypoxia is a key factor promoting the progression of TIF. Loss of microvasculature, reduced oxygen dispersion, and metabolic abnormality of cells in the kidney are the main causes of the hypoxic state. Hypoxia can, in turn, profoundly affect the tubular epithelial cells, endothelial cells, pericytes, fibroblasts, inflammatory cells, and progenitor cells. In this chapter, we reviewed the critical roles of hypoxia in the pathophysiology of TIF and discussed the potential of anti-hypoxia as its promising therapeutic target.

Renal fibrosis: Primacy of the proximal tubule

Tubulointerstitial fibrosis (TIF) is the hallmark of chronic kidney disease and best predictor of renal survival. Many different cell types contribute to TIF progression including tubular epithelial cells, myofibroblasts, endothelia, and inflammatory cells. Previously, most of the attention has centered on myofibroblasts given their central importance in extracellular matrix production. However, emerging data focuses on how the response of the proximal tubule, a specialized epithelial segment vulnerable to injury, plays a central role in TIF progression. Several proximal tubular responses such as de-differentiation, cell cycle changes, autophagy, and metabolic changes may be adaptive initially, but can lead to maladaptive responses that promote TIF both through autocrine and paracrine effects. This review discusses the current paradigm of TIF progression and the increasingly important role of the proximal tubule in promoting TIF both in tubulointerstitial and glomerular injuries. A better understanding and appreciation of the role of the proximal tubule in TIF has important implications for therapeutic strategies to halt chronic kidney disease progression.

Preparation and renoprotective effects of carboxymethyl chitosan oligosaccharide on adriamycin nephropathy

Carboxymethyl chitosan oligosaccharide (CMCOS), the hydrolytic product of carboxymethyl chitosan, is nontoxic, easily absorbable and good antioxidant. In this study, CMCOS was prepared and its properties in adriamycin nephropathy therapy were investigated. Our results showed that CMCOS had good curative effects on renal function and parenchymal injury induced by adriamycin. CMCOS administration significantly relieved symptoms of proteinuria, hypoalbuminemia, hyperlipidemia, renal hyperplasia and histological lesions in rats (P < 0.01). Further exploration for the underlying mechanisms indicated that CMCOS treatment reduced macrophage accumulation, myofibroblast transdifferentiation and podocyte apoptosis. CMCOS treatment could regulate secretions of cytokines (IL-1β, TNF-ɑ and TGF-β1) and improve activities of antioxidative enzymes (SOD, GSH-Px) (P < 0.01). In conclusion, therapeutic effects of CMCOS on renal injury mediated by inflammation, fibrosis and oxidative stress made it a good kidney health product and a promising candidate in clinical treatment of human chronic kidney disease.

Cobalt treatment does not prevent glomerular morphological alterations in type 1 diabetic rats

Early renal morphological alterations including glomerular hypertrophy and mesangial expansion occur in diabetic kidney disease and correlate with various clinical manifestations of diabetes. The present study was designed to investigate the influence of pharmacological modulation of HIF-1α (hypoxia inducible factor-1 alpha) protein levels, on these glomerular changes in rodent model of type 1 diabetes. Male wistar rats were made diabetic (Streptozotocin 45 mg/kg; i.p.) and afterwards treated with HIF activator cobalt chloride for 4 weeks. Renal function was assessed by serum creatinine, albumin, proteinuria levels, oxidative stress: reduced glutathione levels and catalase activity, and renal tissue HIF-1α protein levels were determined by ELISA assay. Histological analysis of kidney sections was done by haematoxylin and eosin (glomeruli diameter), periodic acid Schiff (mesangial expansion and glomerulosclerosis) and sirius red (fibrosis, tubular dilation) staining. Diabetes rats displayed reduced serum albumin levels, marked proteinuria, lower kidney reduced glutathione content, glomerular hypertrophy, glomerulosclerosis, mesangial expansion, tubular dilation and renal fibrosis. Cobalt chloride treatment normalised renal HIF-1α protein levels, reduced development of proteinuria and tubulo-interstitial fibrosis, but the glomerular morphological alterations such as glomerulosclerosis, mesangial expansion, increased glomerular diameter and tubular vacoulations were not abrogated in diabetic kidneys. Glomerular morphological abnormalities might precede the development of proteinuria and renal fibrosis in experimental model of type 1 diabetes. Pharmacological modulation of renal HIF-1α protein levels does not influence glomerular and tubular dilatory changes in diabetic kidney disease.

High glucose up-regulates microRNA-34a-5p to aggravate fibrosis by targeting SIRT1 in HK-2 cells

Tubulointerstitial fibrosis (TIF) is crucial in the development of renal fibrosis in diabetic nephropathy(DN). Previous data shows that SIRT1 plays an important role on fibrosis, but the effect on TIF in DN and underlying mechanisms remains uncertain. In this study, we evaluated the vital role of SIRT1 and identified SIRT1 as a downstream target gene of microRNA-34a-5p (miR-34a-5p) in TIF of DN. The result revealed that expression of miR-34a-5p, fibronectin(FN),collagen type I (COL1) and transforming growth factor β1 (TGF-β1) were up-regulated accompanied by the corresponding down-regulation of SIRT1 in renal tissues of high fat diet and streptozotocin(HFD/STZ)induced diabetic mice with DN, and that the SIRT1 mRNA level was negatively correlated with miR-34a-5p expression in high glucose stimulated human proximal tubule cell line(HK-2) cells. We then demonstrated that overexpression of SIRT1 reduced, whereas small interfering RNA targeting SIRT1 enhanced the expressions of TGF-β1 and fibrosis-related genes including FN and COL1 in HK-2 cells. Furthermore, we identified that miR-34a-5p directly suppressed SIRT1 to increase the profibrogenic effects of TGFβ1 through targeting the 3'untranslated region of SIRT1. The functional correlation of miR-34a-5p induced SIRT1 decrease was supported by overexpression and inhibition of miR-34a-5p in HK-2 cells. All the results reveal that SIRT1 which is vital in the evolution of renal TIF in DN can be directly suppressed by miR-34a-5p, and suggest that miR-34a-5p is a new target for DN treatment.

Matrix Metalloproteinases in Kidney Disease: Role in Pathogenesis and Potential as a Therapeutic Target

Matrix metalloproteinases (MMPs) are large family of proteinases. In addition to a fundamental role in the remodeling of the extracellular matrix, they also cleave a number of cell surface proteins and are involved in multiple cellular processes. MMP activity is regulated via numerous mechanisms, including inhibition by endogenous tissue inhibitors of metalloproteinases (TIMPs). Similar to MMPs, a role for TIMPs has been established in multiple cell signaling pathways. Aberrant expression of MMPs and TIMPS in renal pathophysiology has long been recognized, and with the generation of specific knockout mice, the mechanistic role of several MMPs and TIMPs is becoming more understood and has revealed both pathogenic and protective roles. This chapter will focus on the expression and localization of MMPs and TIMPs in the kidney, as well as summarizing the current information linking these proteins to acute kidney injury and chronic kidney disease. In addition, we will summarize studies suggesting that MMPs and TIMPs may be biomarkers of renal dysfunction and represent novel therapeutic targets to attenuate kidney disease.

Zinc Attenuates Tubulointerstitial Fibrosis in Diabetic Nephropathy Via Inhibition of HIF Through PI-3K Signaling

Evidence has demonstrated that hypoxia may have a central pathogenic mechanism in the development of diabetic nephropathy (DN). Epithelial-to-mesenchymal transition (EMT) of mature tubular epithelial cells in kidney is a contributor to the renal accumulation of matrix protein in DN and is highly associated with the progression of tubulointerstitial fibrosis. Zinc (Zn) has anti-fibrosis effects in liver and lungs. In the present study, we aimed to investigate the effect of Zn on renal tubulointerstitial fibrosis especially under hypoxic conditions and its association with DN. We found that Zn treatment blockaded tubular EMT and attenuated renal tubulointerstitial fibrosis by downregulation of hypoxia-inducible factor alpha (HIF-1α) in the kidneys of diabetic streptozotocin-treated mice. High glucose (HG)/hypoxic conditions stimulated EMT in renal tubular cells as indicated by the significant decrease in epithelial marker E-cadherin and ZO-1 while the increase in mesenchymal markers α-smooth muscle actin (α-SMA). Zn supplement mainly prevented HG/hypoxic-induced HIF-1α accumulation and EMT marker changes. In co-treatment Zn with PI3K/Akt/GSK-3β signaling pathway, inhibitor LY294002 prevented HG/hypoxic-induced HIF-1α increase and EMT changes, suggesting that Zn may mediate HG/hypoxic-induced EMT through PI3K/Akt/GSK-3β pathway. Therefore, we concluded that Zn had an important anti-fibrosis role under HG/hypoxic conditions, and a novel mechanism contributing to Zn protection on renal tubular epithelial cells from HG/hypoxia-induced EMT through activation of PI3K/Akt/GSK-3β signaling pathway, which subsequently leads to the downregulation of the expression of HIF-1α.

Response gene to complement 32 regulates the G2/M phase checkpoint during renal tubular epithelial cell repair

Background

The aim of this study was to evaluate the influence of RGC-32 (response gene to complement 32) on cell cycle progression in renal tubular epithelial cell injury.

Methods

NRK-52E cells with overexpressed or silenced RGC-32 were constructed via transient transfection with RGC-32 expression plasmid and RGC-32 siRNA plasmid, and the cell cycle distribution was determined. The expression levels of fibrosis factors, including smooth muscle action (α-SMA), fibronectin (FN) and E-cadherin, were assessed in cells with silenced RGC-32.

Results

The cells were injured via TNF-α treatment, and the injury was detectable by the enhanced expression of neutrophil gelatinase-associated lipocalin (NGAL). RGC-32 expression also increased significantly. The number of cells at G2/M phase increased dramatically in RGC-32 silenced cells, indicating that RGC-32 silencing induced G2/M arrest. In addition, after treatment with TNF-α, the NRK-52E cells with silenced RGC-32 showed significantly increased expression of α-SMA and FN, but decreased expression of E-cadherin.

Conclusions

The results of this study suggest that RGC-32 probably has an important impact on the repair process of renal tubular epithelial cells in vitro by regulating the G2/M phase checkpoint, cell fibrosis and cell adhesion. However, the exact mechanism needs to be further elucidated.

Glycated albumin triggers fibrosis and apoptosis via an NADPH oxidase/Nox4-MAPK pathway-dependent mechanism in renal proximal tubular cells

Glycated albumin (GA), an Amadori product used as a marker of hyperglycemia and the early-stage glycation products compared to AGEs, might further promote kidney lesions in diabetic nephropathy (DN). However, the mechanisms how GA cause proximal tubular cells damage remain poorly understood. In this study, we investigated the effects of GA on fibrosis and apoptosis of renal proximal tubular cells (NRK-52E) in vitro experiments. Our results showed that GA promoted α-SMA, fibronectin (FN) and TGF-β expressions in NRK-52E cells. GA also increased cell apoptosis and stimulated the expressions of pro-caspase 3/cleaved-caspase 3. GA overloading enhanced the phosphorylation of MAPK pathway. GA-induced α-SMA, FN, TGF-β and caspase 3 expressions were completely suppressed by the NADPH oxidase inhibitor apocynin (Apo), the reactive oxygen species (ROS) scavenger N-acetylcysteine (NAC) and the latent antioxidant Astragaloside IV (AS-IV). Real-time PCR showed that GA increased Nox1, Nox2 and Nox4 mRNA expressions, especially the Nox4 expression. Furthermore, Nox4 siRNA blocked GA-induced tubular damages and the MAPK pathway activation. These results demonstrate that GA increases the permissiveness of proximal tubular cells to fibrosis and apoptosis in vitro by triggering a pathway that involves NADPH oxidase/Nox4-MAPK signaling pathway. This event may represent a key cellular effect in increasing the susceptibility of tubular cells to fibrosis and apoptosis when the tubules cope with a high GA load. This effect is instrumental to renal damage and disease progression in patients with DN.

Ureic clearance granule, alleviates renal dysfunction and tubulointerstitial fibrosis by promoting extracellular matrix degradation in renal failure rats, compared with enalapril

ETHNOPHARMACOLOGICAL RELEVANCE

Chinese herbal compound prescription has a unique therapeutic action on chronic kidney disease (CKD) in China. In clinics, Uremic Clearance Granules (UCG), a compounded Chinese patent medicine, has been frequently used to treat chronic renal failure (CRF) patients for nearly 30 years, however, the deep therapeutic mechanisms involved in vivo remain a challenge. This study aims to demonstrate the effects and mechanisms of UCG on renal dysfunction and tubulointerstitial fibrosis by regulating extracellular matrix (ECM) degradation and transforming growth factor (TGF)-beta1/Smad signaling activity in vivo, compared with enalapril.

MATERIALS AND METHODS

Twenty-six rats were randomly divided into 4 groups, a sham-operated group (Sham group), a vehicle-intervened group (Vehicle group), a UCG-treated group (UCG group) (5g/kg/day) and an enalapril-treated group (Enalapril group) (20mg/kg/day). The rats with renal failure were induced by adenine (150 mg/kg/day) and unilateral ureteral obstruction (UUO), and killed on day 35 after the administration. Proteinuria, urinary N-acetyl-beta-D-glucosaminidase (UNAG), blood biochemical parameters, renal morphological changes, collagen type IV (CIV), matrix metalloproteinase (MMP)-2, MMP-9 and tissue inhibitors of metalloproteinase (TIMP)-1, as well as the key molecular protein expressions in TGF-beta1/Smad signaling pathway were observed, respectively.

RESULTS

Adenine administration and UUO induced severe renal damages, as indicated by renal dysfunction, proteinuria and the marked histopathological injuries in the tubules and interstitium, which were associated with MMP-2/TIMP-1 imbalance and TGF-beta1/Smad signaling activity, as shown by up-regulation of the protein expressions of TGF-beta1, TGF-beta receptor type I (RI), TGF-beta receptor type II (RII), Smad2/3, phosphorylated-Smad2/3 (p-Smad2/3) and Smad4, as well as down-regulation of the protein expression of Smad7 in the kidney. UCG treatment, however, significantly not only attenuated renal dysfunction and tubulointerstitial fibrosis, but also improved the protein expressions of MMP-2, TIMP-1, TGF-beta1, TGF-beta RI, p-Smad2/3, Smad4 and Smad7 in the kidney. Besides, the effects of UCG were stronger than those of enalapril partly.

CONCLUSION

UCG similar to enalapril, is renoprotective via ameliorating renal dysfunction and tubulointerstitial fibrosis in the renal failure model. The potential mechanisms by which UCG exerts its therapeutical effects in vivo are through promoting ECM degradation and regulating MMP-2/TIMP-1 balance or signaling molecular activity in TGF-beta1/Smad pathway in the kidney. These findings suggest that UCG treatment is undoubtedly useful in preventing the progression of CRF.